Description Related to Prior Art
When light beam illuminated on the retina through cornea, pupil, lens and vitreous body, molecules of photopigment of the photoreceptors on the retina excited by this light beam will be deformed and hence, generate a current flow as illustrated by Wald G. in his literature in 1968--Molecular basis of Visual Excitation. Science 162, 230-239, and by Penn R. D. et al in their literature in 1969--Signal Transmission along retinal rod and the Origin of the Electroretinographic a-wave. Nature 223, 201-205. This deformed molecules of photopigment will be no longer in possession of its original character to accept light excitation and therefore, requires a period of time plus a series of chemical reactions before to be recovered to its origin, such as described in an article written by Stryer L -Cyclic GMP cascade of Vision, Annu. Rev. Neurosc. 9, 87-119, 1986--or, by Pugh E. N. et al.--Visual transduction in Vertebrate rods and cones, Vision Res. 26(10), 1613-1643, 1986--and by Fung, B. K. K.--Transducin: structure, function and the role in phototransduction. In "progress in retinal research" chap. 6, Persimmon Press, Oxford 1987. Alpern, M A & Krantz, DH-visual pigment kinetics in abnormalities of the uvea-retinal epithelium interface in man, Invest. Ophthalmal and Vis. Sci. 20, 183, 1979.
For the ordinary person, after the photoreceptor was excited by different light intensity by a period of time, the deformed molecules of photopigment thereon may return to its original form. The average capability of its recovery shall be effected by the micro-environment and this is what we called "metabolic activity". Based on the study made by Alpern M A et. al. ("Visual Pigment kinetics in abnormalities of the uvea-retinal epithelium interface in Man", Invest Ophthalmic and Vis Sci, 20: 83, 1979) the retinal pigment epithelium is one of the most active areas on the human body in metabolism. Apparently, under some conditions, the influence of this metabolic activity will lead the observer to have different color match under different brightness of light beam. This difference shall also appeared on the observer's retina, which accordingly, indicated whether its metabolic activity is normal or abnormal.
However, the micro-environment during the course of its recovery undertake by these molecules somehow will effect the rate thereof. That is to say; if the strength of light increases, the amount of deformed photopigment molecules needed to be recovered will correspondingly increase. To speak as a whole, the metabolic activity effected by this micro-environment is bound to have a change. Consequently, sensitivity to color change for a person under test shall also be changed accordingly, so is the difference of color matching caused by this change occurred. The stronger the light applied to retina, the great the difference in color matching appeared from the person under test whose metabolic activity is abnormal. This is because we usually are unable to take a direct measurement to the rate of metabolism on the bottom portion of human eye, but to re-laid on a method of measurement which can provide an indirect way to indicate its metabolism.
So far as we know, there are the following patent priorities proposed to use methods of color matching such as Moreland's match or Rayleigh match to identify the anomalous color vision of a person taking the test: ROC Patent No. 36290-Four Light Channel anomaloscope. Japanese Patent No. 1735230, and U.S. Pat. No. 4,966,453. However, the principle used by the present invention is completely different from the above three patent priorities and is more delicate in construction and novel in designing. The greatest difference is that the present invention can detect the dynamic change of the photopigment density along with the changing retinal illuminances. This is also the first one to use a TV monitor to directly reflect the observer's eyeball image during the course of test in comparison with U.S. Pat. No. 4,966,453. The anomaloscope of the present invention can produce more uniform project light than that of the above U.S. patent.